1. Field of Invention
The present invention relates to a new method of testing and evaluating physical moisture retention of tobacco.
2. Description of Related Arts
The moisture retention of cigarettes has a rather close relationship with the quality of the cigarettes, and the particular study on fragrance enhancement and moisture retention of cigarettes is important in the Mid-Term and Long-Term Science and Technology Development Plan of tobacco industry. A problem firstly encountered in studying the moisture retention of the cigarettes is how to test and evaluate the moisture retention accurately and conveniently. Currently, the following evaluation method is commonly used. Specifically, a cut tobacco sample without any humectant and a cut tobacco sample with humectants added are put into a drier having a saturated saline solution inside or a thermo-hygrostat and then are weighed periodically. Next, moisture contents of the samples at different time points are calculated by using an oven method and compared by drawing a graph. However, the above evaluation method generally has the following disadvantages. (1) The testing period is long, and the method is complicated. The testing method generally needs 3 to 5 days to enable the tobacco samples to reach equilibrium moisture content, and requires large numbers of repeated manual operations. (2) The tobacco belongs to colloid capillary porous thin-layer materials and has a relatively strong water absorbability, so the testing result tends to be affected by operators and operating environments, therefore causing that the result may not be accurate and has poor reproducibility. (3) Only some discontinuous data points are obtained which fail to reflect tiny changes in the moisture contents of the tobacco samples against time, therefore making it difficult to investigate dynamic rules of moisture desorption or moisture absorption of the cut tobacco. Accordingly, it is urgent to provide a new method of testing the moisture retention of tobacco logically and effectively.
On the other hand, various novel dynamic vapor sorption (DVS) instruments are being constantly developed, and have been successfully applied in various related fields such as pharmaceutical industry, food industry, and material industry. The instruments can control relative humidity and temperature of tested samples accurately and conveniently, and have greatly improved precision and accuracy in comparison with the conventional method using the saturated saline solution.